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Embryology > Gastrulation, Neurulation (wk 3) > Flashcards

Gastrulation, Neurulation (wk 3) Flashcards

1
Q

Gastrulation is the beginnings of

A

Morphogenesis

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2
Q

What occurs during gastrulation?

A

Changes to the bilaminar disc

  • appearance of the primitive streak
  • development of the notochord and prechoridal plate
  • differentiation into 3 germ layers
    - trilaminar embryonic disc
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3
Q

Once the trilaminar disc is formed, what is the embryo referred to as

A

A gastrula

Week 3 development

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4
Q

Germ Layers (3):

A

Ectoderm
Mesoderm
Endoderm

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5
Q

Ectoderm

A

Surface ectoderm-epidermis

Neuroectoderm - CNS, PNS, retina

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6
Q

Mesoderm

A

Skeletal and smooth muscle, CT., most of cardio system, blood cells, bone marrow, reproductive and excretory organs

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7
Q

3 parts of the mesoderm

A 
Paraxial = somites
Intermediate = genitourinary systems
Lateral = body walls
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8
Q

Endoderm

A

Epithelium of respiratory and GI systems, including glands

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9
Q

Primitive streak is what

A

A thickened linear band of epiblast

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10
Q

The primitive streak begins where

A

Caudally in the median plane of the embryonic disc

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11
Q

The primitive streak is formed by what

A

A migration of epiblast cells to the median plane of the embryonic disc

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12
Q

What happens when the primitive streak elongates

A

The cranial end enlarges to form the primitive node and the primitive groove

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13
Q

The primitive groove ends in a small depression which is called the

A

Primitive pit

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14
Q

Epiblast cells migrate through the primitive groove to become the

A

Endoderm and mesoderm

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15
Q

All of the primitive stuff together forms the embryo’s

A

Craniocaudal axis

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16
Q

Cells from the deep surface of the primitive streak forms the embryonic connective tissue known as

A

Mesenchyme

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17
Q

Mesenchyme forms many types of cells:

A

Fibroblasts
Chondroblasts
Osteoblasts

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18
Q

The primitive streak decreases in size and becomes an insignficant structure where

A

In the sacrococcygeal region of the embro (wk 4)

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19
Q

The prechordial plate forms when
What is it?
What is it the site of?

A

Day 14
Endodermal cells in a localized area that form a thickened circular area
This is the site of the mouth

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20
Q

Notochordal process forms when

A

Day 16-17

Mesenchymal cells form a cord called the notochordal process

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21
Q

As the notochordal process grows cranially it develops a lumen called

A

The notochordal canal

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22
Q

The notochordal process continues to grow until

A

It reaches the prechordal plate

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23
Q

What does the notochord provide

A

Defines the axis of the embryo
Gives it rigidity
Serves as the basis for development of the axial skeleton

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24
Q

The future site of the vertebral bodies form around what

A

The notochord
The notochord deteriorates as the vertebral bodies form
Remains as the nucleus pulposus

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25
Q

What induces neural plate formation

A

The notochord

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26
Q

How does the mesoderm and endoderm form?

A

Epiblast cells pass through the primitive streak

Triggered by embryonic growth factors

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27
Q

3 types of mesoderm:

A

Paraxial =somites
Intermediate = genitourinary systems
Lateral = body walls

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28
Q

Oropharyngeal membrane is formed how?
What does it prevent?
Future site of?

A

Formed from the prechordal plate

The endoderm and ectoderm fuse

Prevents the notochordal process from continuing cranially

Future site of the mouth

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29
Q

The cloacal membrane forms where and is the future site of what?

A

Forms caudally to the primitive streak

Site of future anus

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30
Q

Cardiogenic area is what?

A

Premordium of the heart

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31
Q

Allantosis appears when?
Shape?
Involved with?
Forms what?

A

Appears approx day 16

Sausage shaped - extends from caudal wall of umbilical vesicle to the connecting stalk

Involved with early blood formation

Forms the early urinary bladder

The vessels become unbilical arteries and veins

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32
Q

The neural plate forms from the thickening of what?

Forms the?

A

The notochord growth induces the embryonic ectoderm thickens forming the neural plate

Forms the CNS - neuroectoderm

33
Q

Neural grove forms when, how, and what?

A

Day 18

Neural plate opens in center

Neural folds form on each side of grove

Beginning of the brain!

34
Q

Neural tube begins forming when?

A

End of week 3

Neural folds come together and fuse

Folic acid plays a part in this

35
Q

Neural crest cells fuse to form what

A

The neural crest between the neural tube and ectoderm

36
Q

Somites begin forming when?

How?

Forms what?

A

Begin forming end of week 3

The paraxial mesoderm begins dividing into paired cube shaped bodies called somites - around the neural tube

Starts in the occipital region

Forms most of the axial skeleton - associated with musculature and dermis

37
Q

Each somite is innervated by what?

A

1 individual spinal nerve

39
Q

Somites differentiate into 2 regions:

A

Sclerotome - ventraomedial part, form axial skeleton

Dermomyotome - dorsolateral part w/ 2 regions

40
Q

Myotomes and dermatomes of the same somite are innervated by what

A

The same spinal nerve

41
Q

Myotomes differentiate into two regions:

A

Epaxial - muscle innervated by dorsal primary rami, deep muscles of the back

Hypaxial - muscle innervated by ventral primary rami, all other muscles

42
Q

Each individual spinal nerve separates into what

A

Dorsal and ventral primary rami just outside of the IFV

43
Q

Lateral mesoderm forms the

A

Body walls

44
Q

Lateral mesoderm differentiation causes the development of the

A

Intraembryonic coelom

  • small coelomic spaces in lateral mesoderm and cardiogenic mesoderm forming a single horseshoe shaped cavity
45
Q

Development of the intraembryonic coelom divides the lateral mesoderm into 2 layers called:

A

Somatopleure - the somatic or parietal

Splancnopleure - splanchnic or visceral

46
Q

When does the circulatory system begin?

A

Beginning of wk3

47
Q

When does uteroplacental circulation begin

A

Wk 5

48
Q

Angiogenesis begins where?

When?

A

Begins in the extraembryonic mesoderm of the umbilical vesicle, chorion, connecting stalk

Wk3

49
Q

Mesnechymal cells differentiate into

A

Angioblasts

50
Q

Angioblasts form clusters known as

A

Blood islands

51
Q

Angioblasts flatten to form what

A

Primitive endothelial cells

52
Q

The mesenchymal cells that surround the primordial endothelial blood vessels differentiate into what

A

The muscular and connective tissue elements of the vessels

53
Q

Vasculogenesis is the formation of

A

New vascular channels by assembly of individual cell precursors (angioblasts)

54
Q

Primordial blood cells develop from hematopoietic progenitor that form from specialized endothelial cells of vessels called

A

Hemangioblasts - located on the umbilical vesicle and allantois

55
Q

What is hematogenesis

When does it begin

Where does it begin

A

Blood formation

Week 5

Beginning in liver, then in spleen, bone marrow, lymph nodes

56
Q

Mesenchymal tissue in cardiogenic area forms what

A

Heart and great vessels

57
Q

Primitive heart tube contains what and forms what

A

Contains endothelium-lined channels = endocardial tubes

Fuse to form a primordial heart tube

58
Q

How does the primordial cardiovascular system form?

A

The tubular heart joins with blood vessels in the embryo, connecting stalk, chorion, and umbilical vesicle

59
Q

What is the first organ system functioning?

A

At end of week 3 the blood is circulating and heart is beating

60
Q

Trancus arterious

A

Premordium of the aorta and pulmonary trunk

61
Q

Bulbus cordis

A

Forms the primitive ventricle and part of the aorta

62
Q

Sinus venosus

A

Premordium of the SCV IVC some coronary veins and atria

63
Q

Development of chorionic villi

A

Early wk 3

Mesenchyme grows into the primary villi

Forms a core of loose connective tissue

This is secondary villi

64
Q

When do primary chorionic villi appear?

A

At end of second week

Cytrotrophoblastic cells produce cellular extensions that grow into the overlying syncytiotrophoblast forming it

65
Q

What happens to mesenchymal cells in the secondary villi?

A

They differentiate into both capillaries and blood vessels

66
Q

When capillaries become visible the villi are called

A

Tertiary chorionic villi

67
Q

The capillaries fuse to form

A

Arteriocappillary networks

68
Q

The capillary network is connected to the embryonic heart by vessels that differentiate from what

A

The mesenchymne of the chorion and connecting stalk

69
Q

Lacunae does what

A

The maternal blood flows into it

Oxygen and nutrients are passed to the embryo tissues over the surface of synchytiotrophoblast

70
Q

Oxygenated blood passes into the lacunae from what

A

The spiral endometrial arteries in the endometrium

71
Q

Deoxygenated blood is removed from the lacunae through what

A

Endometrial veins

72
Q

When is fetal blood flow established

A

End of 3rd week

73
Q

Heartbeat is present at day what

A

21-22

74
Q

When can the heartbeat be detected

A

During 4th week

75
Q

Cytotrophoblastic shell is formed by what?

A

Cytotrophoblastic cells of the chorionic villi

76
Q

Main stem chorionic villi

A

Attach the villi to the endometrium

77
Q

Branch chorionic villi grow from

A

The sides of the main stem chorionic villi

78
Q

Most of the exchange of material between blood of the mother and the embryo takes place through

A

the walls of the branch chorionic villi

79
Q

2 regions of the dorsolateral part, aka the dermomyotome

A

Myotome - myoblast - form muscle

Dermatome - fibroblast - form dermis

Embryology (4 decks)

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